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Jun 19, 2026 · Fundamentals

Understanding C++ Multiple Inheritance: What Goes Into the A and B Parts of a vtable

The article explains how clang can dump the exact vtable layout for a class with multiple inheritance, revealing that a single vtable is actually a virtual table group composed of a primary and secondary table, each containing its own offset_to_top, RTTI entries, function slots and thunks, and shows why new virtual functions appear only in the primary part while the secondary part holds adjusted thunks for overridden base functions.